Most drugs are classified into hydrophobic and hydrophilic drugs. Hydrophobic drugs exhibit limited solubility in an aqueous solution, and thus are difficult to be effectively delivered in vivo. Hydrophilic drugs exhibit excellent initial expression of drug effects due to high solubility, but encounter difficulties in continuous drug release, and thus require frequent drug administration. To overcome these difficulties, development of various drug delivery carriers using nanoparticles has continued, and studies on polymeric drug delivery carriers, lipid drug delivery carriers, and nano tubes are actively progressing. As a polymeric drug delivery carrier, a polymer-drug conjugate, a polymer micelle, or a dendrimer is used.
However, such drug delivery carriers exhibit fast drug release due to instability in an aqueous solution, and particularly, when an hydrophilic drug or protein drug and antibodies are loaded, fast drug release is induced due to excellent solubility in an aqueous solution, thereby making it difficult to realize desired drug effects. To overcome this problem, repeated drug administration is required, and in the case of an expensive protein drug or antibody, an increase in treatment cost is expected.
Meanwhile, since a liposome may be composed of several kinds of lipid molecules, and most phospholipids constituting the liposome are not toxic or harmful to a human body, it is receiving attention as an effective drug delivery carrier. In Korean Patent Publication No. 0792557, liposome-type nanoparticles prepared and used as a drug delivery carrier are disclosed.
However, physical stability is not ensured in particles using a liposome, and therefore various studies to ensure stability have been attempted. For example, a specific surfactant was added to a liposome to induce an increase in stability, electrostatic charge lipids were added to components for a liposome, or sterols, anionic lipids or spingo lipids were introduced. To this end, studies to enhance stability of a liposome have been continuously performed, but the techniques have not exhibited sufficient physical stability, and thus utilization in the pharmaceutical field has been limited.
Therefore, development of new types of biocompatible particles which may increase safety in an aqueous solution, maintain an excellent redistribution function in the aqueous solution when prepared in a powder type, and flexibly control a drug release rate, thereby exhibiting a continuous drug release pattern, is required.